filedialog.askopenfilename returns 'Open(**options).show()'.  IDLE's File => Open (^O) calls Open and show directly.  It continues to run on all versions on my machine (and presumably those of numerous others).  I have TortoiseGit now and only recently removed TortoiseHG, so those two seem well-enough behaved.  This is almost certainly not a cpython issue, but it would be good to know where the problem lies.